FMF mod author says the error is on the picker tweaks side so I'm here now.
From my post on his forum:
~~~~~~~~~
Seems like FMF has a conflict with other mods I use that work fine. any ideas?
Version: FluidMustFlow_1.2.8
other mods:
Enhanced_Map_Colors_1.5.3
PickerAtheneum_1.2.2
PickerTweaks_2.2.2
Loading error: https://imgur.com/a/Tl9HElY